Electrical filament support device



Jan. 21, 1969 E. ROWE 3,423,622

ELECTRICAL FILAMENT SUPPORT DEVICE Filed July 5, 1966 EDWARD ROWE 1N VEN TOR.

BY ROBERTS, CUSHMAN a GROVER ATTORNEYS United States Patent 2 Claims This invention relates to electrical devices such as incandescent lamps, electron discharge tubes and similar devices having a coiled filament carrying current at high power.

One example of a high power device is an incandescent iodine quartz lamp having a tungsten coil filament enclosed in a quartz envelope containing a quantity of iodine. Such lamps are commonly operated at one or several kilowatts, and the filament and its lead wire support operate at intense heat producing deformation or relative movement of the filament and support and poor mechanical and electrical contact between them. The filament cannot be welded to the support because the flux necessary for a good weld will contaminate the filament.

Thus it is an object of the present invention to provide an improved mechanical and electrical connection between a filament and its support, which connection will be maintained at high operating temperatures.

According to the invention an electrical device comprises an insulating base, a coiled filament in said base having turns wound around a tubular space, lead wire means mounted .on the base for supporting and making electrical connection with said filament, said lead wire means including a wire having an end fitting in the tubular space inside a plurality of turns of the filament, said Wire end having a portion of reduced cross-section forming a radial shoulder, at least one of said plurality of filament turns being deformed to engage said reduced portion inside said shoulder, and said shoulder facing said turn to oppose withdrawal of the turn from said portion.

For the purpose of illustration a typical embodiment of the invention is shown in the accompanying drawing in which:

FIG. 1 is an elevatoin of an incandescent lamp, partly broken away;

FIG. 2 is an end view of a lead wire support for the filament in the lamp of FIG. 1;

FIG. 3 is a side view of the lead wire support; and

FIG. 4 is an enlarged end view of the support and filament showing the method of assembly.

As shown in FIG. 1 an iodine quartz lamp has a quartz envelope 1 enclosing a coiled coil tungsten filament 2 at each end of the envelope. The ends of the coil coiled filament are electrically and mechanically connected to lead in wires 3 extending into the presses 4 of the quartz envelope 1. Each lead in wire 3 is welded to a molybdenum plate 6 within the press 4, the plate 6 in turn being welded to a terminal wire 7 extending outside the press 4.

A typical filament for a 2000 watt iodine quartz lamp is made of a 1390 mm. length of 0.018 inch diameter tungsten wire wound around an 0.055 inch diameter mandrel at 36 turns per inch. This primary coiling is then wound again around an 0.265 inch diameter mandrel at 6.5 turns per inch to yield a coil with 5.6 secondary turns.

As shown in FIGS. 2 to 4, the lead in wire 3 comprises a shank 8 and a hooked end 9 which terminates in a curve matching the arc of the secondary turns of the coil 2. The hooked end 9 is inserted into the primary coiling of the filament for 14 to 16 turns, and for this purpose is made of approximately 0.055 inch diameter tungsten wire permitting it to fit within the primary turns of the filament 2.

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According to the invention the hooked end 9 of the lead in wire 3 has a recess .or portion 11 of reduced crosssection about at the mid-joint of the hooked portion 9. The recess portion 11 forms two shoulders 12, the outermost shoulder on the hook facing away from the end of the hooked portion. As shown in FIG. 4 the hooked portion 9 is inserted into about 14 to 16 primary turns of the filament 2. Those primary turns around the recess portion 11 are then hot-pressed so that they lie within the recess portion 11 inside the shoulders 12. The turns are hot-pressed between an anvil 13 and a ram 14 of an arbor press, the ram and anvil being connected to a power supply 16 by a switch 17. Current through the anvil and ram and the filament turns therebetween resistively heats the turns so as to permanently deform them into the recess portion 11. After attaching lead-in wire supports 3 at each end of the filament the filament is assembled in the envelope 1 by conventional methods.

A filament so assembled on recessed lead-in wires is securely held by the hook 9 under deformation stresses of extremely high temperatures. The recessed shoulder 12 at the end of the hooked portion 9 opposes withdrawal of the turns within the recess from the recess, while the outermost coil turns are supported by the full diameter of the end of the hooked portion.

While one desirable embodiment of the invention has herein been disclosed by way of example, it is to be understood that the invention is broadly inclusive of any and all modifications falling within the terms of the appended claims.

I claim:

1. An electrical device comprising an insulating base, a coiled filament in said base having turns wound around a tubular space, lead wire means mounted on the base for supporting and making electrical connection with said filament, said lead wire means including a wire having an end fitting in the tubular space inside a plurality of turns of the filament, said wire end having a portion of reduced cross-section forming a radial shoulder, at least one of said plurality of filament turns being deformed to engage said reduced portion inside said shoulder, and said shoulder facing said turn to oppose withdrawal of the turn from said portion.

2. A high power incandescent lamp comprising an envelope, a coiled filament in said envelope having turns wound around a tubular space, lead wire means mounted in the envelope for supporting and making electrical connection with said filament, said lead wire means including a wire having an end fitting in a tubular space inside a plurality of turns of the filament, said wire end having a recess portion of reduced cross-section forming a pair of radial shoulders, at least one of said plurality of filament t-urns being deformed to lie in said portion between said shoulders, and one of said shoulders facing said turn to oppose withdrawal of the turn from said portion.

References Cited UNITED STATES PATENTS 2,126,155 8/1938 Van Dyck 313144 X 2,141,933 12/1938 Derrott 313-344 X 2,394,474 2/ 1946 Peters 313344 2,424,518 7/ 1947 Stuart 313-344 2,916,653 12/1959 Macksoud 313-344 X JOHN W. HUCKERT, Primary Examiner.

A. 1. JAMES, Assistant Examiner.

U.S. Cl. X.R. 

1. AN ELECTRICAL DEVICE COMPRISING AN INSULATING BASE, A COILED FILAMENT IN SAID BASE HAVING TURNS WOUND AROUND A TUBUALR SPACE, LEAD WIRE MEANS MOUNTED ON THE BASE FOR SUPPORTING AND MAKING ELECTRICAL CONNECTION WITH SAID FILAMENT, SAID LEAD WIRE MEANS INCLUDING A WIRE HAVING AN END FITTING IN THE TUBULAR SPACE INSIDE A PLURALITY OF TURNS OF THE FILAMENT, SAID WIRE END HAVING A PORTION OF REDUCED CROSS-SECTIONN FORMING A RADIAL SHOULDER, AT LEAST ONE OF SAID PLURALITY OF FILAMENT TURNS BEING DEFORMED TO ENGAGE SAID REDUCED PORTION INSIDE SAID SHOULDER, AND SAID SHOULDER FACING SAID TURN TO OPPOSE WITHDRAWAL OF THE TURN FROM SAID PORTION. 